This application is related to and claims priority from Japanese Patent Applications No. 2002-60734 filed on Mar. 6, 2002 and No. 2002-182869 filed on Jun. 24, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a heat storage system for a vehicle, which stores heat by using waste heat from the vehicle. The heat storage system includes an adsorbent for adsorbing and desorbing a medium. The heat storage system is suitably used for a heating system of a vehicle engine, and is also suitably used for a vehicle air conditioner.
2. Description of Related Art
In a system disclosed in JP-A-1-267346, waste heat, generated in traveling of a vehicle, is chemically absorbed while reaction gas is emitted, so that the waste heat is chemically stored. When operation of a vehicle engine is started, the reaction gas is adsorbed, so that the chemically stored heat is emitted to enhance warm-up operation of the vehicle engine. However, the system is only for performing the warm-up operation, and the absorption heat (stored heat) is not effectively used.
In view of the foregoing problems, it is an object of the present invention to provide a heat storage system for a vehicle, which can effectively use adsorption heat.
It is another object of the present invention to improve fuel-consumption efficiency when the heat storage system including a refrigerator is used for a vehicle air conditioner.
According to the present invention, in a heat storage system for a vehicle, an adsorbent for adsorbing and desorbing medium has a medium-adsorbing capacity that is reduced in accordance with a temperature increase of the adsorbent, and generates heat when adsorbing gas medium. The heat storage system includes an adsorption chamber for containing the adsorbent therein, a waste heat supplier that supplies waste heat generated in the vehicle to the adsorbent, an adsorption heat supplier that supplies the heat generated by the adsorbent to an apparatus requiring warm-up operation, and a refrigerator for cooling air to be blown into a passenger compartment of a vehicle. The refrigerator includes a refrigerant-medium heat exchanger for performing heat-exchange between the medium and refrigerant circulated in the refrigerator. In addition, the heat storage system includes a first valve for opening and closing a first passage through the gas medium desorbed from the adsorbent is introduced from the adsorption chamber to the refrigerant-medium heat exchanger, a liquid-medium storage chamber for storing liquid medium cooled and condensed in the refrigerant-medium heat exchanger, and a second valve for opening and closing a second passage through which the liquid-medium storage chamber and the adsorption chamber communicate with each other. Here, the liquid medium is heated and vaporized to be gas medium in the refrigerant-medium heat exchanger by absorbing heat. In the heat storage system, the first valve opens the first passage for a predetermined time when a temperature of the apparatus is equal to or higher than a predetermined temperature, and closes the first passage after the predetermined time passes. Further, the second valve opens the second passage at least when the temperature of the apparatus is lower than the predetermined temperature.
Accordingly, when the first valve opens the first passage, the adsorbent is heated, and the medium adsorbed on the adsorbent is desorbed from the adsorbent. Therefore, the desorbed medium flows to the refrigerant-medium heat exchanger, so that the waste heat is chemically stored as the liquid medium. When the second valve is opened, the refrigerant in the refrigerator is cooled while the chemically stored heat is supplied to the apparatus as adsorption heat. Thus, the waste heat is chemically stored by using an adsorption function of the adsorbent. When the temperature of the apparatus is low as in warm-up operation of the apparatus, motive power consumed by the refrigerator can be reduced while the warm-up operation is enhanced by supplying the adsorption heat to the apparatus. Therefore, the adsorption heat can be effectively used.
Preferably, the refrigerant-medium heat exchanger performs heat-exchange between the refrigerant and the liquid medium stored in the liquid-medium storage chamber when the second valve opens the second passage. Therefore, liquid medium in the liquid-medium storage chamber absorbs heat from the refrigerant through the refrigerant-medium heat exchanger, and is continuously evaporated.
More preferably, the heat storage system includes an adsorbent cooling unit that cools the adsorbent when the second valve opens the second passage. Therefore, consumed power in the refrigerator can be reduced in long time. Here, a radiation portion of the adsorbent cooling unit can be integrated with a radiator for performing a heat exchange between cooling water circulating in the apparatus and outside air.
For example, in a heat storage system, the refrigerant-medium heat exchanger is disposed to cool the refrigerant in the refrigerator through the medium in a cooling mode. Therefore, cooling capacity of the refrigerator can be increased without increasing the rotation speed of a driving device of the refrigerator. Thus, cooling capacity for cooling the passenger compartment can be improved while fuel consumption efficiency can be improved, when the heat storage system is used for a vehicle air conditioner.
Specifically, the refrigerant-medium heat exchanger is disposed to cool refrigerant at a low pressure side after being decompressed in the refrigerator in the cooling mode. For example, when the refrigerator includes at least two heat exchangers at the low pressure side, the refrigerant-medium heat exchanger is disposed in a refrigerant passage connecting the two heat exchangers to cool refrigerant flowing in the refrigerant passage. In this case, the two heat exchangers and the refrigerant-medium heat exchanger can be integrated with each other, or can be disposed separately from each other.
Alternatively, the refrigerant-medium heat exchanger is disposed to cool refrigerant at a high pressure side before being decompressed in the refrigerator, in the cooling mode. In this case, because the refrigerant pressure at the high pressure side can be reduced, the enthalpy and the dryness of refrigerant at an inlet of a low-pressure side heat exchanger can be reduced, and the cooling capacity of the refrigerator can be effectively improved.